(feat) integrated md-datepicker and enabled it in the Preferences module (Vacation)

The date picker suffers from this bug: https://github.com/angular/material/issues/4192

Which makes it not that usable right now.

UI/WebServerResources/scss/components/datepicker/_extends-calendar.scss

@@ -0,0 +1,2 @@
+/*! datepicker/_extends.scss - */
+@import '../../../angular-material/src/components/datepicker/calendar.scss';

UI/WebServerResources/scss/components/datepicker/_extends-datePicker.scss

@@ -0,0 +1,2 @@
+/*! datepicker/_extends.scss - */
+@import '../../../angular-material/src/components/datepicker/datePicker.scss';

UI/WebServerResources/scss/components/datepicker/calendar.scss

@@ -0,0 +1,2 @@
+/// calendar.scss -*- Mode: scss; indent-tabs-mode: nil; basic-offset: 2 -*-
+@import 'extends-calendar';

UI/WebServerResources/scss/components/datepicker/datePicker.scss

@@ -0,0 +1,2 @@
+/// datePicker.scss -*- Mode: scss; indent-tabs-mode: nil; basic-offset: 2 -*-
+@import 'extends-datePicker';

UI/WebServerResources/scss/components/menu/menu.scss

@@ -1,2 +1,2 @@
-/// menu..scss -*- Mode: scss; indent-tabs-mode: nil; basic-offset: 2 -*-
+/// menu.scss -*- Mode: scss; indent-tabs-mode: nil; basic-offset: 2 -*-
 @import 'extends';